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• Obesity is a significant health problem in the United States.  In an attempt to lose weight, many individuals are turning to dietary supplements.  Laboratory studies have shown that the catechins in green tea can inhibit an enzyme, COMT, which normally degrades norepinepherine, a neurotransmitter that has effects on thermogenesis and fat metabolism.  In addition, the caffeine contained in green tea is also known to promote thermogenesis.

• A 1999 study at the University of Geneva compared green tea extract vs. caffeine vs. placebo in a double-blind study evaluating energy expenditure and fat oxidation in healthy men.  The group consuming green tea extract showed an increase in fat metabolism and a slight decrease in carbohydrate metabolism, with a net result favoring increased energy expenditure.

• A 2002 study evaluated the use of green tea extract containing 25% catechins in obese individuals.  In laboratory studies, the extract was shown to inhibit gastric and pancreatic lipases and to increase thermogenesis.  The individuals in this study showed a median decrease in weight of 4.6% and waist circumference of 4.5% after using the supplement for 3 months.

• In order to consume the amount of catechins used in these studies, one would have to consume large numbers of cups of green tea.  The encapsulated form of the extract would be more convenient, but would deliver a very large dose of caffeine, which is presumed responsible for the side effects.

• The authors note that the use of green tea or green tea must be incorporated into a more comprehensive weight-loss program including proper diet and exercise.

• CONCLUSION:  Since few trials have been done examining the role of green tea in weight loss, there is a need for larger, randomized trials.  Once longer and more extensive studies are done, it is possible that green tea extract may prove to be a safer alternative to ephedra for weight loss.